The present invention relates to a ratio control of a continuously variable transmission of an automobile, and more particularly to a traction control by appropriately setting a reduction ratio upon the vehicle starting from a standstill on a road with a low friction coefficient.
Japanese patent application First (unexamined) Publication No. 64-36532 discloses a continuously variable transmission provided with a manual selector switch. According to this continuously variable transmission, if he/she recognizes that a road has a low friction coefficient, the driver places this switch to a predetermined position, causing the transmission to establish a predetermined reduction ratio smaller than the maximum reduction ratio.
An object of the present invention is to improve a ratio control of a continuously variable transmission such that the transmission automatically selects an appropriate reduction ratio for a road condition.